Method and apparatus for adjusting the sensing threshold of a cardiac rhythm management device

Abstract

A method and apparatus for automatically adjusting the sensing threshold of cardiac rhythm management devices. The invention is particularly suited for implementation in devices such as implantable cardiac pacemakers and implantable cardioverter / defibrillators. A method and apparatus are provided in which a noise level and signal level for a sensing channel are determined for each cardiac cycle with the sensing threshold of the channel being adjusted in accordance therewith.

Description

FIELD OF THE INVENTION This invention relates generally to a cardiac rhythm management device such as implantable cardiac pacemakers and implantable cardiac defibrillators. In particular the invention pertains to methods and apparatus for automatically adjusting the sensing threshold of such devices. BACKGROUND Currently available implantable cardiac rhythm management devices, including bradycardia and tachycardia pacemakers and cardiac defibrillators, have sense amplifier circuits for amplifying and filtering electrogram signals picked up by electrodes placed in or on the heart and which are coupled by suitable leads to the implantable cardiac rhythm management device. In most devices, the signals emanating from the sense amplifier are applied to one input of a comparator circuit whose other input is connected to a source of reference potential. Only when an electrogram signal from the sense amplifier exceeds the reference potential threshold will it be treated as a detected card...

AI Technical Summary

Problems solved by technology

In the case of a programmable cardiac rhythm management device the prescribing physician can change the threshold potential of the comparator, but in spite of the flexibility which the programmable threshold offers, malsensing of cardiac depolarization will still occur frequently enough to result in patient discomfort and / or deleterious health effects.

Lead movement and noise may further impede the detection of cardiac depolarization events.

When the peak amplitudes associated with cardiac depolarization events become too small relative to a programmed threshold, or when noise levels in the electrocardiogram approach the sensing threshold, the likelihood of oversensing increases (i.e., false detection of depolarization events).

If the sensing threshold is increased too high in an attempt to overcome the effects of noise, on the other hand, the likelihood of undersensing (i.e., failing to detect depolarization events) is increased.

Images